


Happy Birthday, Zim!

by MetalMistress



Series: Invader Zim: After The Florpus [21]
Category: Invader Zim
Genre: Alien Biology, Alien Character(s), Alien Cultural Differences, Alien Culture, Alien Sex, Alien Technology, Alien Tentacle Cock, Alien Tentacle Dick, Aliens, Birthday, Birthday Fluff, Birthday Party, Birthday Presents, Birthday Sex, Birthday Smut, Domestic Fluff, F/M, Family Fluff, Fluff, Fluff and Humor, Fluff and Smut, Not an Irken, Reader loves Zim and would do anything to make him happy, Romantic Fluff, Smeets (Invader Zim), Tooth-Rotting Fluff, YEEEEEAAAAH BUDDY, Zim gets shy, Zim gets some birthday lovin, Zim has never had a birthday before, Zur loves his dad, poor baby, reader is an alien
Language: English
Status: Completed
Published: 2020-01-19
Updated: 2020-01-19
Packaged: 2021-02-27 11:13:59
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,569
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22286167
Author URL: https://archiveofourown.org/users/MetalMistress/pseuds/MetalMistress
Summary: It's Zim's birthday! WOO-HOO!
Relationships: Zim (Invader Zim)/Reader
Series: Invader Zim: After The Florpus [21]
Series URL: https://archiveofourown.org/series/1543243
Comments: 17
Kudos: 38





	Happy Birthday, Zim!

**Author's Note:**

> Hiiii babies!
> 
> This idea came to me when I was thinking about birthdays that are coming up in my family. Then I went on here to spell-check my work, and then I thought; "Yo! What if Zim celebrates his birthday with his family?!"
> 
> Tell me what you guys think!!

You couldn't believe your ears.

Or well. Inner ears. You lacked outer ears.

**BUT THAT'S NOT THE POINT.**

The point is that you just could not believe what Zim had just told you last night!

Zur's birthday was coming up soon, now that he was roughly a year old in alien terms. You had been hanging out with Zim in the basement as he conducted research on humanity when you asked him for ideas for Zur's birthday party. When Zim told you he had none, you asked him why. Surely, him of all people would have some ideas. He could build the greatest machines, create elaborate plans at the drop of a hat, and yet he couldn't come up with an idea for a smeet's birthday party? Why? So you asked him why he couldn't, and he explained it wouldn't be proper, as he had no experience in that field. Confused, you asked him to elaborate. He hesitated for a split second... then he told you what he meant, and you almost cried.

_Zim had never celebrated his birthday._

In the 150+ years he's been alive, he's never _once_ celebrated his birthday! Your heart broke and ached for him, and although it hurt to hear that, you could understand why upon pausing to think about it. Birthday parties required family and friends, which Zim has never truly had until now. It's not like he had anyone previously to really care and dote on him until you came along.

Zim's previous life was really depressing now that you think about it.

That simply wouldn't do.

So, this morning you had a plan. By the time you had woken up, Zim had already gone down the the basement to work; you could hear him shouting at GIR to get out of the way through the air vents in the hallway. Good, he was distracted. Normally on mornings like this, you'd head right down to him, but you had work to do, and you'd need an extra pair of hands to do it!

So you went right to your son's room.

You knocked on his door, and waited for him to answer.

"Come in!" He shouts.

You enter, and smile at him as he sits up in bed. 

"Hey kiddo. Did I wake you?"

"No, Mama. I've been awake. Floor is too cold, didn't want to get out of bed yet."

You snort. You've done that before. "Want me to get you some boots then?"

He nods, so you run over by his door and grab a pair of black boots for him to wear. When you run back over to him and hand them to him, he quickly puts them on.

When he slides out of bed, he's already wearing his own modified Irken Uniform. It looks just like Zim's, except his has a cut out for his wings. He looks adorable!

You smile and kneel so you're face level with him.

"Hey hun?"

"Yes Mama?"

"I need your help with something."

"Really? Me?" His eyes go all wide and bright.

"Yep! You see, I found out something pretty sad last night. You know how your birthday is coming up? Well, your dad has never celebrated his own birthday... And he's 150, maybe 160."

Zur's curious expression turns to one of horror. "Oh no! That's horrible! That's such a long time..." He trails off, sadly.

"Right?! The thing is, I never was able to find out the date of his birthday or what kind of things he likes. I need you to be sneaky, and ask him for me. Think of it like a mission, just like the ones Mommy told you about. Can you do that for me?"

"YES!" He bounces excitedly as he grabs your hands to hold them. 

You giggle and hush him. "Shhhh, don't want to reveal our plan, do we?"

"Oh, right. Sneaky!" He giggles. 

You smile and press a kiss to his forehead. "Okay. Go find out. Come to my room afterwards, and let me know."

Zur nods, and dashes off to the basement.

* * *

When Zur arrives to the basement, he passes GIR with a wave. GIR waves back and heads back up, likely to watch TV.

"Hi Daddy!" Zur says with a bright smile as he walks up to Zim, who seems to be building something.

"Zur? Is that you?" Zim asks as he pulls up his Welder's mask.

"Yep! It's me!"

Zim smiles down at him, and sets aside his tools. He's unsurprised to see Zur. The boy has a wild curiosity, and likes to ask questions about _everything._

"Whatcha makin, Daddy?"

"I'm repairing something for the Queen. What are _you_ doing, my smeet?"

"I was just wondering what you were doing." Zur says with a smile. "Can I hug you?"

Zim nods, kneels, and opens his arms up for a hug. Excited to get affection, Zur runs right over to him and nearly tackles him into an embrace. He giggles as Zim tries to stabilize himself, who nearly rocks onto his back upon impact.

"Irk, you're getting strong. We'll need to start training you soon.." He murmurs. 

Zur smiles, brimming with happy energy. Then he pauses and tilts his head. "Hey, Dad?"

"Yes?"

"I know Mommy's birthday, but I don't know yours." He tilts his head, scrunching up his face in thought. "When is your birthday?"

Zim, who chalks the question up to nothing more than his child's growing curiosity for life, answers. "My birthday is actually tomorrow."

"Tomorrow? How old will you be?"

"I'll be 162."

"Wow! That's amazing!"

Zim chuckles at his smeet's excitement. "I suppose so, yes."

"I was wondering, what are birthdays like?"

"You mean.. traditions?"

"Yes. What will my birthday be like?"

"Well, let's see..." Zim says, scratching his chin in thought. "Irken traditional birthdays... You'll have to forgive me, it's... something I'm not too familiar with, but for your sake I'll try to remember!"

Zur nods understandingly, listening intently.

"Well... I believe Irkens usually celebrate their birthdays with their families and friends, just like Vexens do. Usually there is cake, and sweets. Sometimes presents, if the irken desires something."

"What would YOU want on your birthday?"

"Me? Well.. I.. I think I'd..." Zim swallows thickly, surprised by such a question. "I've always wanted a cake...Chocolate, to be precise..." He pauses, but then waves his hand dismissively before he gets too emotional; "But that's not important! What's important is that _you,_ my wonderful smeet, are going to be one year old!" Zim says, expertly deflecting the focus back onto his son.

Zur smiles, leaning into his father's hands as he caresses his face. 

"I fear I may not tell it to you enough, but I hope you know that I love you." Zim murmurs softly down to Zur.

"I love you too, Daddy. I think I'm going to go wake up Mama."

"Oh? She's still asleep? She must be tired..."

Zur nods. "I'll see you later, Daddy! I love you!"

"I love you too!"

* * *

Zur bursts into your bedroom and closes the door behind him, all while giggling maniacally. 

"I suppose it went well?" You chuckle, as he scrambles up the bedsheets.

"Daddy'sbirthdayistomorrow! He'sturning162! Hewantschocolatecake!" Zur spits out all in one breath.

"Woah, woah woah. Slow it down a little bit." You laugh. "Say that again, but slower. Take a deep breath first."

Zur nods, taking a slow, deep breath to calm himself down. Then he explains; "Daddy's turning 162 tomorrow."

"Tomorrow?! That green buttmunch, he-! he must have planned to not mention it to me so I'd think it was just a normal day..."

"Is that bad, Mama?"

"Oh no, sweetheart. You need to understand, before you and I came into your father's life, he was very... troubled. He's probably embarrassed about it."

"Ohhh."

"But now that we're here." You grin widely, squishing Zur's chubby cheeks and making him laugh. "We can make him happy. What do you say? Want to do a little shopping?"

"YES!"

You hush him and hold him close, pressing your forehead against his with a wide smile on your faces. 

"I love you, Zur."

"I love you too, Mama!"

Your already wide smile somehow widens even more. "Alright! Let's get going. Get your coat, it's cold outside!"

You spent most of the day being sneaky and making the chocolate cake that Zur had said Zim wanted. You were able to prepare everything and hide it for tomorrow. You called Dib, and explained your plan to surprise Zim, and of course he was down for it. You went to bed that night, giddy and excited.

Then, morning came.

When Zim woke up, the first thing he noticed was that you were not in bed beside him.

"Life-Mate?" He sleepily grumbles, as he reaches for your empty side of the bed. When he receives no answer, he sits up in bed. 

"Life-Mate?" He calls out again, only louder.

"I'm here, baby!" He hears your cry.

"Where?" He shouts back.

"Out in the living room!"

"Is everything okay?"

"Yeah! But I need your help with something. Can you come here?"

"Yes... Give me a moment to get dressed." Zim says with a yawn. He stretches lazily, and gets out of bed. Mechanical arms reach out of the floor and walls, carrying parts of his uniform. They effortlessly slip them onto his body. He smooths the tunic down his lean torso, and then walks out of the bedroom, and down the hall. He enters the living room, adjusting his gloves as usual, when he looks up and stops in his steps. He stares with shock written all over his face, and his jaw hits the floor.

Standing in the living room, are Zur, GIR, Dib, and You, carrying a large, chocolate cake. There is a colorful banner that says "Happy Birthday Zim!" in fancy script. There are candles on the cake that spell out "162". The candles are lit, and the flame dances, lighting up your face. "Happy Birthday!" everyone cries out happily.

"W-...Wha-? How?" He stutters.

"Happy birthday, baby."

"How did... How did you know?" He looks at you with confusion. When you nod towards Zur, Zim looks down at his son, who has a wide, naughty smirk across his lips.

"Happy birthday, Daddy! Try some of the cake! Mommy and I made it!"

Zim nods softly, his eyes still wide and jaw still slack. He's completely surprised. He mindlessly walks over to the couch and sits down. You set the cake down on the coffee table, and cut out a small slice, put it on a plate, and hand it to Zim. He takes a fork, and cuts off a small piece, and puts it in his mouth to taste it. As soon as the piece hits his tongue, his eyes widen even more. The air is tense. He chews slowly on it, and then swallows it. His jaw hangs open, and then his eyes fill with tears.

"Baby?" You ask softly, concerned. Zim looks up at you, and tears just roll down his cheeks at a rapid pace. He reaches up for you, and you quickly rush over to embrace him. He holds you tightly, pressing his face into your neck, and he just _sobs_ tears of joy.

"That... that's the best.. that's the best cake I've... I've ever had. Thank you so much. I love you, I love you so, so much.." He murmurs quietly into your inner ear. You smile, and rub his back lovingly. 

When he pulls away, Zur has run over and places his hand on his father's leg, worry on his face. His worry turns to surprise when Zim suddenly scoops him up into his arms, and tickles the ever-living hell out of him. Zur squeals and wriggles in his arms, trying to get away. 

"Daddy! Hahahaha, Daddy noooo!"

"You are the best! Yes you are! You are all the best family I could ever ask for!" Zim cackles, as he mercilessly tickles his son.

Even Gir makes the mistake of coming to close, and even _he_ is promptly scooped up and tickled. GIR squeals and laughs maniacally as he thrashes wildly in Zim's grasp.

Once he has set GIR down beside Zur on the couch, Dib approaches, but is staying a fair distance away from Zim. Zim notices and snorts; "I am _not_ tickling you."

"Duly noted." Dib says, with a wide mischievous grin.

Everyone sits down, happily chatting while eating pieces of cake. The focus is on Zim, as he retells his crazy experiences where he caused chaos within the Irken Armada. Everyone laughs, and everyone is happy. It's great!

After cake, everyone gives their presents to Zim. Zur gives him something he made in school, which makes Zim puff out his chest with pride. GIR gives him something he baked, specifically chocolate cupcakes. Dib gives Zim a new high-tech tool set. You give Zim a card that shows Zim was bought a full-on Vexen Spa experience at one of the highest quality spas on the Hive, all expenses paid for. Zim nearly starts bawling all over again as everyone hands him their presents, but he is able to maintain his composure. 

"Thank you. All of you." Zim says with a shy, appreciative smile. Everyone nods, turning back to chat with each other. Zim leans over to you, where he whispers into your ear; "You especially. You sly minx, I bet you planned all of this."

You grin wickedly and nod. "I did."

He presses a loving kiss to your temple, and you flatten your antennae shyly at the affection. 

"Happy Birthday, baby." 

♥

* * *

Later, at night, you've just finished tucking in Zur and GIR into their beds and are ready for the final phase of your plan.

You stroll into your bedroom, where Zim is sitting up in bed reading. You close the door quietly behind you, lock it, and press a few buttons to activate the sound-proofing. A soft 'beep' lets you know it's been activated, and the sound grabs Zim's attention, who raises his head to look at you. You lean against the door, with a naughty smirk across your lips. Your eyes are partly lidded, and you are just oozing sex appeal. Zim bookmarks his place in his book and sets it aside. "Yes...?" He swallows thickly.

"Are you ready for your final present?" You purr.

"Present? I wasn't aware that you had another for me..."

"Of course. What's a birthday without some birthday sex?"

Zim's eyes widen. _"Oh..._ Oh yes, please." He swallows once more, and leans back in bed.

You take your time undressing, unzipping your bodysuit down the front. Zim whimpers at the sight of your skin. Despite having seen you naked before, it always excites him to watch you undress.

Slowly, your hips sway as you stroll over to the bed as Zim kicks back the covers, hurriedly undressing himself. Climbing up onto it on all fours, you slink your way up Zim's legs until you are face level with his cock. It's hard, and throbs eagerly under your attention. You glance back up at Zim, and maintain eye contact with him as you lower your head and take his length into your mouth. He softly moans, as he watches you engulf him. Your warm, wet tongue curls around his throbbing member, and he shivers at the contact. 

"Fuck." He whispers softly before biting his lip.

You moan against him, the vibrations sending pleasure throughout his groin.

"Fuck!" He repeats, whispering harshly this time. You begin to slowly bob your head, making Zim roll his eyes into the back of his head as he closes them. He rolls his head back, sighing in relief. He shivers and shudders occasionally, a familiar warm feeling slowly building within his stomach. His cheeks flush, and his breathing picks up ever so slightly. He grasps the bed sheets within his hands, and pulls on them ever so slightly as he lets out a soft, little whine.

You pick up the pace a little.

He begins to roll his hips upward into your mouth, in short, small little bursts, working in tandem with you as you continue to suck him off.

"Yes...." He breathes out, completely letting himself become lost in pleasure. "Ah..."

You suddenly take him deeper into your mouth and trill softly, sending another wave of vibrations through his cock. He gasps loudly, stilling his movement just as he thrusts his hips upward into your mouth. You retaliate by taking him deeper, now full-on deep-throating him. You can feel his cock throb within your throat, and it makes you gag a little, but you're able to recover. Slowly, you work yourself up to a steady pace, taking it slow so you don't overwhelm yourself and your gag reflex. Zim whines loudly of the feeling, and grips the bed sheets tighter as he begins to speak softly but very fast in a desperate tone;

"please, oh please don't stop. Please, for the love of Irk, don't stop." He whines.

You reply by humming against him, causing him to cry out and thrust up in surprise. You gag, but recover once more. Once you are comfortable, you pick up the pace, now sucking him off at a rapid pace.

"yes, oh yes, oh yesssss" He moans breathily, all while panting like a dog. "Ohh! if you don't stop soon, I'm going to cum." He says with a whimper.

You suddenly speed up, causing him to suddenly gasp, and then curse loudly in Irken. He becomes overwhelmed by lust and gently grasps the sides of your head, and begins to thoroughly face-fuck you. You take it, and allow him to do as he pleases. His moans increase in pitch, and it isn't long before he cums down your throat. Like a good girl, you swallow every last drop.

He collapses beneath you, and pants heavily. He finally opens his eyes and sees you sitting up, wiping off a little bit of cum that dribbled out of your mouth. He moans at the sight, and has a full-body shiver in response.

"Did you enjoy yourself?" You giggle.

"Very, very much so. However, I'm not done. I still want to..." He pauses and then growls lustfully; "bury myself within you. But I need to recover. Come up here."

You follow his command, and slide yourself up his body, straddling his waist. He cranes his neck up and immediately takes one of your nipples into his mouth. His tongue teases the areola, tickling it and covering it in his slick saliva. It shoots a warm feeling down your spine and straight to your cunt. Your wings flutter as pleasure begins to take over your body, as Zim relentlessly suckles on it. You moan, and gasp above him loudly, as your nipples are very sensitive. It isn't long before you can feel his cock throb against your pussy lips, and you are shocked at how quickly he recovered. Suddenly, he lifts your hips, and then slides you down onto his dick. You arch your back, moaning along with him as the two of you become very still, giving your cunt time to accommodate his girth. 

"J-Jeez, Zim." You whine, feeling him throb against your g-spot.

"Sorry, I- _ohh-_ I just needed to be buried inside of you... Ohh _fuck!"_ He hisses as he braces his feet against the bed, and begins to wildly thrust up into you. Crying out, you press your hands against the wall, legs shaking as he continues to fuck himself up into your dripping cunt. Lust quickly overwhelms the pair of you, and all you are able to do is hold on for dear life as Zim grips your hips in a death grip and begins to raise you up and drop you down onto his cock, all while still rocking his hips up into you. He thrusts into you like a wild animal, growling, moaning and snarling in absolute erotic euphoria. He doesn't even have time to warn you that he's close, and neither do you, because all of a sudden you're both cumming. He lets out a pornographic moan as he cums inside of you, his balls twitching as they empty themselves. Your walls milk him for all he's worth, as they clench down and squeeze out your juices. 

You collapse on top of him, panting heavily. When you go to move yourself off of him, his arms come up to wrap around your torso. 

"No, don't move. Stay here. Let me hold you." He says tiredly. 

"Okay." You say quietly, enjoying the feeling of his warm arms around you. You press your head against his chest, and you can feel his strong, steady heart beat against your cheek, and you can also hear it in your ear.

"You surprised me, today." He quietly murmurs, as he presses his lips against the top of your head.

"Did I? I hoped so."

"I enjoyed the party. Thank you."

"You're welcome. It's going to be the first of many, in the upcoming years."

Zim smiles widely at that. "What would I do without you, Life-Mate?"

You scoff playfully. "I'm not that wonderful."

"But you are. At least, you are to me." 

You blush deeply; "Thank you, Zim. I love you."

"And I love you." He says softly, nuzzling you closer.

Soon, you fall asleep to the sound of his steady, strong heartbeat. 

♥

**Author's Note:**

> Hello, pets. ♥
> 
> What did you think? What was your favorite part? Do you have a request?  
> Tell me in the comments below, if you so desire to! Don't be shy!


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